Method upgradeOrSchedule_

src/custom-element.js:1248–1296

* Upgrade or schedule element based on R1. * @param {boolean=} opt_disablePreload * @private @final

(opt_disablePreload)

     * @private @final
     */
    upgradeOrSchedule_(opt_disablePreload) {
      if (!this.R1()) {
        this.tryUpgrade_();
        return;
      }

      if (this.mountPromise_) {
        // Already mounting.
        return;
      }

      // Schedule build and mount.
      const scheduler = getSchedulerForDoc(this.getAmpDoc());
      scheduler.schedule(this);
      this.classList.remove('amp-unresolved', 'i-amphtml-unresolved');

      if (this.buildingPromise_) {
        // Already built or building: just needs to be mounted.
        this.setReadyStateInternal(
          this.implClass_ && this.implClass_.usesLoading(this)
            ? ReadyState_Enum.LOADING
            : ReadyState_Enum.MOUNTING
        );
      } else {
        // Not built yet: execute prebuild steps.
        this.setReadyStateInternal(ReadyState_Enum.BUILDING);

        // Schedule preconnects.
        if (!opt_disablePreload) {
          const urls = this.implClass_.getPreconnects(this);
          if (urls && urls.length > 0) {
            // If we do early preconnects we delay them a bit. This is kind of
            // an unfortunate trade off, but it seems faster, because the DOM
            // operations themselves are not free and might delay
            const ampdoc = this.getAmpDoc();
            startupChunk(ampdoc, () => {
              const {win} = ampdoc;
              if (!win) {
                return;
              }
              const preconnect = Services.preconnectFor(win);
              urls.forEach((url) =>
                preconnect.url(ampdoc, url, /* alsoConnecting */ false)
              );
            });
          }
        }
      }
    }

    /**
     * Try to upgrade the element with the provided implementation.